Add LOCATABLE.sequence_id, to be set on all LOCATABLE objects in openEHR systems.
The field type is String, and is of the form 'n.m', where:
n = ordinal number of version in versioned_composition or other versioned container, in which this node was first added.
m = ordinal number of child item, in order of creation.
Examples: "1.3" = 3rd child under a parent node, in 1st version of some Composition.
A node added in version 6 has an id like '6.m'.
In the case of branched version ids, we will have something like:
In branched version structures, if used, clashes in the final part can occur which is desirable to indicate clashes that need to be resolved.
URI syntax: need a short form:
e.g. items[at0003,#1.1] means the 1st child in 1st version. If no #n.m, then follow current behaviour and return all matching (normally = all children).
LOCATABLE.sequence_id will be mandatory.